My problem
I have switched from Windows xp to Windows 7; but now my Windows 7 crashes with blue screen. My pc is running 24h/7 sometimes for 2 to 3 months with no crash. But from 1 week after crash in a loop, it require disconnecting the computer to wait several second before the reboot. I have reinstalled Windows 7 with nothing on it (no other program) but still it crashes repeatedly.

But I am not having any such issues in Ubuntu.

I can see these crashes for 1 ½ years since I bought my pc. For that I have changed a lot of things already. I left that first PC processor and graphics card. But the problem is that this is so random that I hardly can define.

Is it possible that the processor in facing problem to boot Windows because of presence of Ubuntu?

Can you provide the details of error message that you are getting in the "blue screen" that you have? Then I'll tell you how good is an Ultimate Boot CD to pass some tests with your machine: Memory Test (memtest 86 +), processor (OCCT or Burn etc.). Then whether the crash occurs when you do something special on the PC (games? Internet? Nothing particular, it crashes even on the desktop). Finally these are some basics.

Very odd thing! If you do not have crashes under Ubuntu, it seems difficult to blame the hardware! But it does not make some tests. As proposed in previous post you perform some test on memory, processor and HDD! This is a minimum requirement.

For this, we must put your PC config mini, ie the need to remove anything that is not absolutely necessary for startup.